And it’s not just about being more environmentally friendly either. Improving efficiency, in everything from air conditioning and electronics to vehicle engines, also means fewer fuel convoys, which are frequent targets of attack, said Andrew Holland, a former Hagel aid now with the American Security Project.

More efficient engines can also improve the range vehicles of all types and electric or hybrid engines can be quieter than their conventional counterparts.

We in the Defense Department have a role to play here – not solely because we should be good stewards of our environment and our scarce resources but also because there is a strategic imperative for us to reduce risk, improve efficiencies, and preserve our freedom of action whenever we can.